Craig Federighi shows off AirPlay 2 at WWDC 2017

AirPlay is probably your favorite way to stream video from your Mac or iPhone to your Apple TV, but for streaming music, it's got competition.

Bluetooth speakers come in every size, shape, and price point, and on the high end there's multiroom systems from companies like Sonos and Bang & Olufsen. Apple's coming after both of those with AirPlay 2, the next iteration of its streaming protocol.

What is AirPlay 2?

It's a new feature in iOS 11 that lets you send audio to multiple AirPlay speakers at once, from anywhere in iOS. This lets you assemble a multiroom audio system from any compatible speakers, and control it from iOS's AirPlay controls or inside third-party apps.

AirPlay 2 shown in iOS 11 at WWDC 2017

How does it know where your speakers are?

If you have any HomeKit devices, you're probably already using iOS 10's Home app. Now you'll be able to add speakers to the rooms of your home, and then they'll show up in iOS's AirPlay controls as Living Room, Bedroom, Tree House, Man Cave, and so on.

Can I send audio to multiple speakers from my Mac?

AirPlay 2 support is also baked into macOS 10.13, so you'll be able to send music or podcasts to multiple speakers from your Mac as well.

And the Apple TV too?

Yes, once you upgrade to tvOS 11, your Apple TV can send audio to speakers around your home as well. You could put your party playlist on the Apple TV's Music app, play it on the living room speakers plus out on the deck, and control it with the Apple TV remote or iOS app—or with Siri.

AirPlay 2 on the Apple TV

As a bonus, whatever soundbar or speaker system you have connected to the Apple TV become de facto AirPlay 2 speakers. You'll be able to send audio from your iPhone or Mac to your Apple TV and your other speakers at the same time.

What speakers are supported?

Naturally, Apple's just-announced HomePod speaker will support AirPlay 2. But other manufacturers can add support too.

In fact, the HomePod only supports AirPlay 2. You can't stream to it over Bluetooth. Apple Music plays on the HomePod via the cloud, but any other audio you want to send to it has to come over AirPlay 2, from a device running iOS 11, macOS 10.13, or tvOS 11.

So the AirPlay speaker I own now won't work?

It could, after an update. During the keynote, Craig Federighi showed a slide of speaker makers already on board to support AirPlay 2, either with new equipment or a firmware update to existing Wi-Fi equipped AirPlay speakers.

Libratone, maker of the excellent Q Adapt headphones and ZIPP Wi-Fi/Bluetooth/AirPlay speakers, even confirmed on Twitter that it could add AirPlay 2 support to the $269 ZIPP and $199 ZIPP Mini with a firmware update.

What other companies are making AirPlay 2 speakers?

Bose tweeted that a new SoundTouch with AirPlay 2 is "coming soon," and later clarified that other speakers would get an over-the-air update. "More information about compatibility and launch timing will be available at a later time," the company said.

Bang & Olufsen's own multiroom speaker system already supports AirPlay, and offers a variety of shapes, sizes, and price points, but the company is so far mum on if and when those would get AirPlay 2 support.

Another intriguing company is Denon, which makes DJ equipment as well as speakers and headphones. Can you imagine how cool it would be to send your own mixes from your decks to multiple speakers wirelessly, with every beat in sync?

Companies with AirPlay 2 plans.

Other companies teased during the keynote include Apple's own Beats of course, Bose, Bowers & Wilkins, Danish speaker maker Dynaudio, Polk, Definitive Technology, Bluesound, Naim, McIntosh (how apt!), and Devialet.

What about the AirPort Express?

The great thing about Apple's little router is that you could wire it up to some powered speakers and instantly give them AirPlay support. But Apple seems to be backing away from the router business, so it's unclear if the company will bother to push out an update to the Express to support AirPlay 2.

How is this different from Sonos?

Sonos is a great multi-room audio system, but to use it, you have to be in the Sonos app. Most music services are supported, and of course you can play your own music too. But AirPlay 2 will give users more freedom, since any developer can add support to their app, and buyers will be able to choose speakers made by more than one company.

Will apps need to be updated?

iOS 11's AirPlay 2 API, shown at WWDC 2017

Yes. Third-party apps like Spotify and Castro will be able to send audio to multiple speakers once they're updated to support AirPlay 2. And of course you'll need iOS 11 (or tvOS 11 or macOS 10.13) to run those apps.